1. Technical Field
The presently disclosed subject matter relates to a vehicle light, and in particular, to an optical axis adjusting apparatus for use in a vehicle light. The optical axis adjusting apparatus can be configured to reduce the load on the vibrating vehicle body.
2. Description of the Related Art
Conventional optical axis adjusting apparatuses have been known, and one example of which is disclosed in FIG. 1 of Japanese Patent Application Laid-Open No. 2003-187610 (hereinafter, referred to as “the conventional optical axis adjusting apparatus).
FIGS. 1 and 2 show schematic vertical cross-sectional views of the conventional optical axis adjusting apparatus corresponding to FIG. 1 of Japanese Patent Application Laid-Open No. 2003-187610. The conventional optical axis adjusting apparatus is used for a vehicle headlight 910 that includes a lamp housing 911 and a reflector 915, and is configured to include a ball joint 920 via which the lamp housing 911 and the reflector 915 are connected. An aiming screw 911a with root portion 911a1 is supported by the lamp housing 911 so as to freely turn and allows the reflector 915 to rotate with respect to the lamp housing 911 around the ball joint 920. A nut portion 915a is provided on the reflector 915 and can be screwed onto the aiming screw 911a. 
In FIGS. 1 and 2, the reference numeral 912 denotes an outer lens, 913 denotes a socket, and 914 denotes a light source, such as a bulb. Reference 915b denotes a bent portion of the reflector 915, reference 915c denotes an area near the nut portion 915a of the reflector 915, and reference 915d denotes a main body of the reflector 915. In addition, reference 911a2 denotes a tip portion of the aiming screw 911a which is positioned opposite to the root portion 911a1 via the nut portion 915a. 
The conventional optical axis adjusting apparatus for vehicle headlight 910 can be operated as follows. As shown in FIG. 1, the aiming screw 911a can be turned so that the optical axis of the vehicle headlight 910 is adjusted to be lowered. Then, the nut portion 915a of the reflector 915 can move as shown by the arrow A in FIG. 1. Namely, the nut portion 915a is forced to linearly move rearward (to the right side of FIG. 1) along the center axis (along a right-to-left direction in FIG. 1) of the aiming screw 911a as the aiming screw 911a is turned.
In this case, the upper portion of the reflector 915 is pivoted by the ball joint 920, and the area supported by the ball joint 920 can be rotated around the ball joint 920. Accordingly, in reality, the nut portion 915a of the reflector 915 is regulated to move along the arrow B of FIG. 1 in a circular clockwise direction around the ball joint 920 which serves as a center of the circular direction.
In this instance, since the root portion 911a1 of the aiming screw 911a is fixed to the housing 911, a force shown by the arrow C in FIG. 1 is applied to the aiming screw 911a so that the tip portion 911a2 of the aiming screw 911a rotates around the root portion 911a1 which acts as a center in a clockwise direction while a counter force is applied to the reflector 915 in a reverse fashion.
Consider the case in which the aiming screw 911a can be turned so that the optical axis of the vehicle headlight 910 is adjusted soas to be lifted. In this case, the nut portion 915a of the reflector 915 can move as shown by the arrow A in FIG. 2. Namely, the nut portion 915a is forced to linearly move frontward (to the left side of FIG. 2) along the center axis of the aiming screw 911a as the aiming screw 911a is turned.
As described above, in reality, the reflector 915 including the nut portion 915a is regulated to move along the arrow B of FIG. 2 in a circular counterclockwise direction around the ball joint 920 which serves as a center.
In this instance, a force shown by the arrow C in FIG. 2 is applied to the aiming screw 911a so that the tip portion 911a2 of the aiming screw 911a rotates around the root portion 911a1 which acts as a center in a counter-clockwise direction while a counter force is applied to the reflector 915 in a reverse fashion.
In order to release or relax the forces applied to the aiming screw 911a and the reflector 915, as shown in FIGS. 1 and 2, the conventional optical axis adjusting apparatus can be provided with the bent portion 915b. 
Furthermore, as shown in FIGS. 1 and 2, the root portion 911a1 of the aiming screw 911a is constrained by the lamp housing 911 and the tip portion 911a2 is not constrained by the lamp housing 911. In other words, the aiming screw 911a is supported by the lamp housing 911 in a cantilever fashion.
In recent years, as the projector type vehicle headlight design has become popular, the unit that is to be rotated around such a ball joint with respect to a lamp housing has a tendency to increase in weight (see, for example, the vehicle headlight as shown in FIG. 1 of Japanese Patent Application Laid-Open No. 2002-83508).
On the other hand, recent vehicle headlights may include what is known as an Adaptive Front Lighting System (AFS) and can be provided with a swing mechanism such as a swivel motor in order to achieve the AFS function. This configuration also increases the weight of the unit that is to be rotated (see, for example, the vehicle headlight as shown in FIG. 8 of Japanese Patent Application Laid-Open No. 2007-179915).
Accordingly, the structure of the aiming screw which is supported by the lamp housing in a cantilever fashion and the nut portion of the reflector that is to be screwed onto the aiming screw also have a tendency to increase the load these elements should bear.
In FIGS. 1 and 2, if the aiming screw 911a and the nut portion 915a of the reflector were to be arranged within a vertical plane including the ball joint 920, in this case, the unit to be rotated with respect to the lamp housing 911, or the reflector 915, can be supported mainly by the ball joint 920 (among the ball joint 920, the aiming screw 911a and the nut portion 915a of the reflector 915). Accordingly, the load the aiming screw 911a and the nut portion 915a should bear does not become so large. On the contrary, when the aiming screw 911a and the nut portion 915a are arranged outside a vertical plane including the position of the ball joint 920, the load the aiming screw 911a and the nut portion 915a should bear may become large.
FIGS. 3A and 3B show the diagrams corresponding to FIG. 8 of Japanese Patent Application Laid-Open No. 2001-151011. Specifically, FIG. 3A is a schematic horizontal cross-sectional view of another conventional vehicle headlight 910 taken along line A-A of FIG. 3B. FIG. 3B is a front view of the vehicle headlight of FIG. 3A.
In this conventional vehicle headlight 910, the optical axis adjusting apparatus is configured so that an aiming screw 911b is turned in one direction for optical axis adjustment. Then, a nut portion 915e of the reflector 915 is moved forward (to the lower side of FIG. 3A) along the center axis of the aiming screw 911b (in the upper-to-lower direction in FIG. 3A) with respect to the aiming screw 911b. As a result, the reflector 915 itself can rotate around the ball joint 920 which serves as a center with respect to rotation of the lamp housing 911 in a clockwise direction as shown in FIG. 3B. Accordingly, the optical axis of the vehicle headlight 910 can be adjusted leftward in FIG. 3A.
On the other hand, when the aiming screw 911b is turned in the other direction for optical axis adjustment, the nut portion 915e of the reflector 915 is moved rearward (to the upper side of FIG. 3A) along the center axis of the aiming screw 911b with respect to the aiming screw 911b. As a result, the reflector 915 itself can rotate around the ball joint 920 which serves as a center with respect to rotation of the lamp housing 911 in a counter-clockwise direction as shown in FIG. 3A. Accordingly, the optical axis of the vehicle headlight 910 can be adjusted rightward in FIG. 3A.
In this conventional vehicle headlight, as shown in FIGS. 3A and 3B, the aiming screw 911b and the nut portion 915e of the reflector 915 are arranged outside a vertical plane that includes the position of the ball joint 920. As described above, when the vehicle headlight 910 is configured to have a projector type structure or is provided with a swing mechanism such as a swivel motor in order to add the AFS function to the reflector 915, the load that the aiming screw 911b which is supported by the lamp housing 911 in a cantilever fashion and the nut portion 915e of the reflector 915 should bear can become excessively large.